In 1734, Anton Wilhelm Amo, a West African student and former chamber slave of Duke Anton Ulrich of Braunschweig-Wolfenbüttel, defended a philosophy dissertation at the University of Halle in Saxony, written in Latin and entitled “On the Impassivity of the Human Mind.” A dedicatory letter was appended from the rector of the University of Wittenberg, Johannes Gottfried Kraus, who praised “the natural genius” of Africa, its “appreciation for learning,” and its “inestimable contribution to the knowledge of human affairs” and of “divine things.” Kraus placed Amo in a lineage that includes many North African Latin authors of antiquity, such as Terence, Tertullian and St. Augustine.

In the following decade, the Scottish philosopher David Hume would write: “I am apt to suspect the Negroes, and in general all other species of men to be naturally inferior to the whites. There never was any civilized nation of any other complection than white, nor even any individual eminent in action or speculation.”

Hume had not heard of Amo, that much is clear. But we can also detect a tremendous difference between Hume’s understanding of human capacities and that of Kraus: the author of Amo’s dedicatory letter doesn’t even consider the possibility of anchoring what individual human beings are capable of doing to something as arbitrary as “complection.” For Kraus, Amo represents a continent and its long and distinguished history; he does not represent a “race.”

Another two decades on, Immanuel Kant, considered by many to be the greatest philosopher of the modern period, would manage to let slip what is surely the greatest non-sequitur in the history of philosophy: describing a report of something seemingly intelligent that had once been said by an African, Kant dismisses it on the grounds that “this fellow was quite black from head to toe, a clear proof that what he said was stupid.”...